1. Field of the Invention
The present invention relates to a method for adjusting the write speed of data recording devices and apparatus thereof, and particularly to a method for adjusting the write speed of data recording devices and apparatus thereof that dynamically sets the write speed according to the number of buffer underrun events when writing to the recording media.
2. Description of the Related Art
Recently, optical storage media, such as compact disc (CD) and recordable compact disc (CD-R and CD-RW) have a significant standing in the evolution of data storage media. With the development of optical storage media, data can be recorded and backed up into high capacity and light discs, and the optical storage media will take the place of traditional data storage media.
FIG. 1 shows the block diagram of a disc servo system. The optical head 11 reads reflection signal from the disc 10. After the signal is amplified and processed by the RF (Radio Frequency) IC 12, the FE (Focus Error) signal, TE (Track Error) signal and relative data and signals are inputted to DSP (Digital Signal Processor) and micro processor 13.
Then, the micro processor 13 computes servo driver signals by analyzing the received data, and outputs the signals to corresponding servos (Focusing Servo 14, Tracking Servo 15 and Spindle Motor Servo 16) for controlling the actuators (focusing actuator 17, tracking actuator 18, sled motor 19 and spindle motor 20) to ensure the accuracy when reading or writing (recording) data.
In the process of writing recordable discs, the data recording device always gradually raises its write speed from lower speed to the maximum write speed or user defined speed according to the preset time regions. FIG. 2 shows the variation of write speed of conventional data recording devices. As shown in FIG. 2, the write speed is 16 in the time region 0˜t1, the write speed is raised from 16 to 20 in the time region t1˜t2, the write speed is raised from 20 to 24 in the time region t2˜t3 and after time t3, the write speed is raised from 16 to the maximum write speed 32 and kept until recording finish.
In the writing process, data is sent from the hard disk or the CD-ROM drive to the host via IDE (Integrated Drive Electronics) interface at first, then the data is sent to the buffer memory of the data recording device via SCSI (Small Computer System Interface) or IDE interface. Finally, the data recording device writes the data stored in the buffer memory to the recordable disc. Since the data is successively stored on the disc, the writing process of the data recording device must be continuous and no interrupt is allowable. If only one link breaks down, the writing process fails, thus the recordable disc has to be discarded.
One reason for writing failure is buffer underrun, that is the data in buffer memory is insufficient. There are various causes of buffer underrun, such as sectors on the hard disk being distributed in a disorderly fashion, insufficient available space on the hard disk, execution speed of the computer system not fast enough, the read speed of data and the write speed of the data recording device not being identical, or the imperfection of the recordable disc, and others.
A conventional solution to solve buffer underrun is to monitor the state of the buffer. If the data received by the buffer is not enough, the writing process is suspended and the system will register the location. The writing process will reinstate when the data of the buffer is full again.
However, the conventional solution only writes data segments several times, and the causes of buffer underrun are not yet solved. Relocating the optical head to the registered location in the conventional solution will lengthen the whole writing process and consume the lifespan of the data recording device.